1. Field of the Invention
The present invention relates to exposure apparatuses, exposure methods and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method that form a pattern on an object with an energy beam, and a device manufacturing method that uses the exposure apparatus or the exposure method.
2. Description of the Background Art
In a lithography process for manufacturing electron devices such as semiconductor devices (integrated circuits and the like) and liquid crystal display devices, an exposure apparatus such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) or a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner)) is mainly used.
In this type of exposure apparatus, in general, by using a laser interferometer, the position of a wafer stage that holds a substrate to be exposed such as a wafer or a glass plate (hereinafter, generically referred to as a wafer) is measured with the side surface of a barrel of a projection optical system serving as a reference, and position control of the stage with respect to the projection optical system is performed using the measurement results (e.g. refer to U.S. Patent Application Publication No. 2007/0288121). Accordingly, even if the position of the projection optical system finely varies due to vibration or the like, the wafer stage can be made to follow the positional variation with high precision.
However, in the case where the laser interferometer is used to measure the position of the wafer stage with the barrel side surface of the projection optical system serving as a reference, the optical path length of the measurement beam becomes as long as around several hundreds mm or more. Therefore, an error occurs in the measurement values in some cases due to temperature fluctuations (air fluctuations) of the atmosphere generated around the optical path of the measurement beam, and this error becomes a factor of positional deviation of patterns formed on the wafer and overlay error between patterns of a plurality of layers that are layered and formed on the wafer.